Adam SmithSTS.002, Fall 2004, Professor David KaiserPaper 3
William Harvey’s Methodological Legacy
“I profess to learn and teach anatomy not from books but from dissections, not
from the tenets of Philosophers but from the fabric of Nature.”
- William Harvey1
The mainstream use of the experimental method in biology, brought about by
William Harvey, marked the beginning of modern medicine and biology. This paper
discusses the events surrounding William Harvey’s contribution, and attempts to distill a
summary of the current beliefs held by most historians. I do not claim to have a new
discovery to share with historians. Instead, I will attempt to bring clarity to the reader
amongst the many disparate writings which can be hard to piece together without a sharp
eye and extensive reading. Unfortunately, to summarize a large body of knowledge,
some of the details must be left out. This is the problem that faces all historians; Steven
Shapin states in his The Scientific Revolution, “selection is a necessary feature of any
historical story, and there can be no such thing as definitive or exhaustive history.”2
Thus, this paper leaves out some historical information. I hope to provide the
information necessary to obtain a firm understanding of this important historical event,
and I also hope that the interested reader will find the bibliography sufficient to
investigate further. If there is a bias in this paper, it is towards the methodology side of
1 William Harvey, The Circulation of the Blood, and other Writings, translated by Kenneth J. Franklin(London: J. M. Dent, 1990 [1649]), 6.2 Steven Shapin, The Scientific Revolution (Chicago: University of Chicago Press, 1996).
the story. Although we will discuss, specifically, the discovery of the circulation of
blood in the body, most of that discussion will be given to set up the scene for
highlighting the general methodologies.
This paper unfolds in roughly chronological order. First, we will consider the
methodologies in use before William Harvey’s works. Next, we will consider Harvey’s
works, beginning with his specific discoveries, then generalizing about his methodology
and evaluating his predecessors’ impact on his works. We will conclude with a
discussion of how he impacted the future of modern science, and we will find that he
spearheaded the widespread use of experimental methods in biology.
Methodology before Harvey
Though Aristotle used his mind to reason about the world, his reasoning did not
lack real-world observations. He did not put himself in a dark room, disconnect his
senses from the world, and then ponder about logic. Certainly he did think about logic as
abstracted from the wider world (e.g. syllogisms), but that was not the totality of his
studies. The observations he used can be called experiences; they are what every person
living at the time might agree to be true. Shapin states:
“Take, for example, the experience – cited by Aristotle and his followers as evidence that the
earth did not move – that an arrow shot straight up in the air landed about where it started. Or
take the experience that heavy bodies fall, or that the sun sets in the west.”3
This is an important point, worth repeating. Aristotle used observations from the
world. However his observations were restricted to passive, every day experiences; he
did not perform experiments, which can be defined as actively manipulating nature in an
3 Shapin, Revolution, pp. 81
attempt to glean information. Bayon agrees, and describes how experiences were turned
into conclusions: “the ancient sages learnt and then speculated ‘why’ things happened,
relying on existing lore, for which purpose they employed an intellectual method whose
use is not yet superfluous: Logic.”4 In today’s modern world, scientists also use
experience and logic to reason about things; these methods are not flawed. Instead, these
methods were simply not the limit of human capabilities. Aristotle did not utilize
experimentation.
We will see how Harvey brought about the widespread use of experimentation in
biology, but he was not the first person to employ the method. Although Galen
performed dissections and other forms of experimentation, his conclusions were
sometimes correct and other times incorrect. As Bayon states, Galen’s experimental
methodology might not have caught on because of his interpretational errors.
“It remains unclear why experimentation was neglected during so many centuries; even after
that Galen had shown the way in several sound tests, some of them in relation to the flow of
the blood; though it must be admitted that in these his interpretation was erroneous and
performance must have been faulty.”5
For whatever reason, scientists after Galen did not begin to employ experiments.
Even famous scientists around Harvey’s time did not perform active experiments, even
though the method was gaining attention, such as Bacon. “Francis Bacon (1561 – 1629)
who pleaded so engagingly for the merits of ‘Experiments of Light’ had no conception
how to carry out any demonstrative test.”6
4 H. P. Bayon, “The Significance of the Demonstration of the Harveyan Circulation by Experimental Tests,” Isis 33 (Dec., 1941): 452.5 Bayon, “Significance,” 450.6 Bayon, “Significance,” 450.
Certainly the experimental approach, as an improvement over the experience
observation approach, was brewing. However it did not come to fruition until William
Harvey’s works, as we will now discuss.
Harvey’s Discoveries and Methods
Harvey makes many contributions to the study of circulation and respiration in his
work The Circulation of the Blood.7 He discusses pulmonary circulation, proves that
veins and arteries only carry blood, and debunks the notion of transport of blood between
the heart’s ventricles. Most importantly, however, he discovers that blood circulates
around the body and through the heart, opposing the previously held notion that blood is
transmitted from the heart to tissues in the body, where it is absorbed. For clarity and
succinctness our discussion of Harvey’s discoveries and methods will focus on the
circulation of the blood. 8
The opening paragraph to the section on circulation communicates the magnitude
of the jump in scientific knowledge that Harvey is making. “The remaining matters,”
Harvey states, “are so novel and hitherto unmentioned that, in speaking of them, I not
only fear that I may suffer from the ill-will of a few, but dread lest all men turn against
me.”9 Harvey then proceeds to set up his argument. He first lays out three pieces of
experimental observations as his evidence:
7 Harvey, Circulation8 Circulation of the blood can refer to two different concepts. The physical circulation of blood in the body refers to the cycling nature of the physical liquid. The chemical circulation refers to the cyclic oxygenation of the blood in the lungs and de-oxygenation at the tissues. Harvey was concerned with the former.9 Harvey, Circulation, pp. 45.
1. He observes “the symmetry and size of the ventricles of the heart and of the
vessels which enter and leave them (since Nature, who does nothing in vain,
would not purposelessly have given these vessels such relatively large size).”10
2. Furthermore, he points out “the elegant and carefully contrived valves and
fibres and other structural artistry of the heart.”11
3. Finally, he notices “the amount, i.e. of transmitted blood, and the very short
time it took for its transfer, and I also noticed that the juice of the ingested
food could not supply this amount without our having the veins.”12 When he
states that the blood takes a short time to transfer to the parts of the body, he is
implicitly deducing its high speed and thus its large volume of flux through
the heart.
With these pieces of evidence in mind, he deduces his conclusion that blood must
move around the body in a circular way: “I then began to wonder whether it had a
movement, as it were, in a circle.”13 Bayon re-states Harvey’s reasoning succinctly:
“Harvey enforced his reasoning most acutely by calculating the amount of blood that would
pass through the heart in an hour; thus obtaining the conviction that, since the blood could
only flow in one direction – on account of the valves – it must necessarily retrace its course,
because such a large quantity could not possibly disappear into the tissues.”14
Harvey’s discovery is well accepted and widely celebrated. One author boasts of
Harvey, “if you desire to follow the bloud all along every steppe, in its progress from the
10 Harvey, Circulation, pp. 45.11 Harvey, Circulation, pp. 45.12 Harvey, Circulation, pp. 45.13 Harvey, Circulation, pp. 4614 Bayon, “Significance,” 444.
hart round about the body, till it return backe againe to its center, Doctory Haruey who
most acutely teacheth this doctrine must be your guide.”15
One modern historian concludes that if Harvey never existed, then his discoveries
would have still been made within another fifty years.16 The acceptance of Harvey’s
methodology had more important implications for biology and all of science. His method
of gleaning evidence from experiments and employing logic to manipulate that evidence
into valuable conclusions was of utmost importance. Harvey showcases his experimental
method in his writing, saying “I thought particularly long and hard about the results of
my experimental animal dissections and opening the veins, an enquiry that took various
forms.”17 Bayon discusses the implications of Harvey’s method:
“Because Harvey’s De motu cordis was the first published record of the solution of a
biological problem by demonstrative tests, it […] announced the beginning of the
development of medicine from a period of philosophical speculation to one of clinical
observation, anatomical investigation, and application of biological experimentation”18
Harvey’s discovery was the origin of the revolution in biology; his thought
process marked a huge leap in scientific capabilities. We will discuss the implications
and lasting effects in the last section of this paper.
Harvey’s Predecessors
Harvey had an explicit strategy for learning from those who came before him. He
used his predecessors’ conclusions as starting points for his studies, and then used his
experimental method to confirm or correct those conclusions. He explains this in the first 15 Sir Kenelm Digby, Two Treatises, (Paris: G. Blaizot, 1644), 238.16 George Kimball Plochmann, “William Harvey and His Methods,” Studies in the Renaissance 10 (1963): 192-196.17 Harvey, Circulation, pp. 45.18 Bayon, “Significance,” 449.
paragraph of his introduction: “It profits one […] to read what his predecessors have
written […]. For by so doing he can confirm their correct statements, and through
anatomical dissection, manifold experiments, and persistent careful observation emend
their wrong ones.”19 This approach closely resembles the scientific processes employed
today for evolving knowledge.
Historians widely hold three people as Harvey’s main influences: Aristotle,
Galen, and Realdo Colombo. We will discuss each of these people and their influence on
Harvey.
Walter Pagel claims that “Harvey […] was a staunch Aristotelian.”20 Indeed,
Harvey says in another one of his works that “The authority of Aristotle has always
[held] such weight with me that I never think of differing from him inconsiderately.”21
These statements are coincident with Harvey’s stated high level strategy; he employs
Aristotle when it is not contradicted by experimentation. Recall, from above, that
Aristotle used experience observations and logic to reach conclusions. Harvey’s
approach, then, accepts these experience observations and their logical conclusions
except when more active tests or experiments contradict them.22 Harvey also looks to
Aristotle’s works for inspiration. After devising the circulation of the blood, he makes an
analogy: “We have as much right to call this movement of the blood circular as Aristotle
had to say that the air and rain emulate the circular movement of the heavenly bodies.”23
19 Harvey, Circulation, pp. 7.20 Walter Pagel, “William Harvey and the Purpose of Circulation,” Isis 42 (Apr., 1951): 28.21 William Harvey, On Generation, translated by Robert Willis (New York: Johnson Reprint, 1965 [1651]), pp. 87.22 An example of a contradiction, and Harvey’s subsequent disagreement with Aristotle, is given in Harvey, Circulation, pp. 47.23 Harvey, Circulation, pp. 46.
There is more disagreement about Galen’s role in influencing Harvey. As
discussed earlier, many of Galen’s conclusions were wrong. Some historians claim that
Galen’s errors slowed the discovery of truth,24 while other historians assert that Galen
aided Harvey’s studies.25 Both groups are correct. If Galen had not made the errors he
did, then he would have seen that the veins and arteries carry only blood26 and might have
also discovered the circulatory system. However, the correct discoveries that Galen
made, namely the one-way valves that we will discuss shortly, were important to
Harvey’s reasoning. So, while Galen made mistakes that set back biology, he also made
contributions that helped. When asked what brought him to hypothesize about
circulation, Harvey said the valves restricting the flow of blood to one direction were the
catalyst. Robert Boyle recalls this:
“And I remember, that when I asked our famous Harvey … what were the things, that
induced him to think of a circulation of the blood? he answered me, that when he took notice,
that the valves in the veins of so many parts of the body were so placed, that they gave free
passage to the blood towards the heart, but opposed the passage of venal blood the contrary
way; …[the blood] should be sent through the arteries, and return through the veins, whose
valves did not oppose its course that way.”27
Galen discovered the valves that Harvey mentions. Therefore, Fleming
concludes, “The real tribute paid by Harvey to Galen would then consist in
acknowledgement that Galen by his description of the cardiac valves […] had afforded
conclusive evidence of such a circulation for those who cared to see.”28 Fleming then
24 Plochmann takes up this perspective in Plochmann, “Methods,” 194-200.25 Fleming adopts this perspective, and fervently defends it throughout Donald Fleming, “William Harvey and the Pulmonary Circulation,” Isis 46 (Dec., 1955): 319-327.26 Bayon, “Significance,” 450.27 Robert Boyle, A Disquisition about the Final Causes of Natural Things, in Works, ed. Thomas Circh, 2nd ed. (London: 1772), vol. 5, 427.28 Fleming, “Pulmonary Circulation,” 321-322.
defends Galen’s mistakes, claiming that they did not hurt Harvey’s progress. “Galen’s
conception of what happened to the blood in the heart and lungs did not obstruct
Harvey’s work.”29 This latter statement is true; Harvey’s work did come to be, and was
therefore not obstructed. However, Galen’s errors probably slowed Harvey’s progress,
and might have prevented further discoveries aside from the circulation. In the end it is
impossible to determine what would have happened if Galen’s work had been any more
right or any more wrong than it was; these points are all speculation.
What is not speculation, however, is that Harvey used some of Galen’s
conclusions to make new discoveries. In this way, Galen helped Harvey in at least one
instance.
It is fruitful to consider the impacts that Aristotle and Galen had on Harvey,
relative to one-another. As described above, Harvey inherited from Aristotle a tradition
of logical thinking and experience observation. Harvey gained an example of
experimentation from Galen, albeit many of Galen’s conclusions were wrong. These two
sets of lessons learned are orthogonal, and came together nicely for Harvey to form a
very solid base of knowledge and methods to work from. Plochmann expresses this, and
attributes the greater contribution to Aristotle. He says,
“Harvey’s debts to Galen and to men of the Renaissance in matters of observation were no
doubt greater, indeed could hardly help being so; yet the treasure he lifted from Aristotelian
methodology was incomparably more important to the success of his inquiry and his
demonstration”30
Although Plochmann seems convicted that Aristotle’s contributions to Harvey’s
success were greater than those of Galen, once again it is an impossible point to settle.
29 Fleming, “Pulmonary Circulation,” 322.30 Plochmann, “Methods,” 193.
Even if Harvey offered a first-hand opinion on this (he does not), Harvey could be wrong.
For a more elaborated discussion of both sides of the debate, see PlochmannError:
Reference source not found and FlemingError: Reference source not found.
Realdo Colombo was one of Harvey’s contemporaries. Colombo studied under
Vesalius, even though Bayon characterizes Colombo as “a vain boaster, addicted to
plagiarism, and he quarreled with Vesalius.”31 Nevertheless, Colombo had significant
achievements. According to Bayon:
“[Colombo] was the first to combine the results of clinical observation, anatomical
dissections, and experimental tests on dogs, so as to deduce a correct interpretation of the
heart-through-the lung-to-heart circuit. […] For this reason Colombo may be considered a
true precursor of Harvey.”32
Harvey, as with Aristotle and Galen, evaluated Colombo’s studies and absorbed
what he could from them. Harvey highlights errors made in some of Colombo’s
conclusions,33 but also acknowledges Colombo’s correct ideas.34
There were others who claimed to have discovered circulation before Harvey, but
all of these have been adequately disputed.35
In conclusion of this section, Harvey draws from the works of many scientists
who preceded him. However, he only uses those works as starting points in his studies;
he used experiments to arrive at his ultimate conclusions. Thus, standing on the
shoulders of those giants gave him an enormous head start, but his methodology allowed
him to rely on the right conclusions and make progress in the right direction.
31 Bayon, “Significance,” 446.32 Bayon, “Significance,” 446.33 Harvey, Circulation, pp. 9.34 Harvey, Circulation, pp. 12.35 For more discussion on these cases, see Bayon, “Significance,” 446-448.
Harvey’s Legacy - Scientific Effects
Contrary to what we might have hoped for, Harvey’s methodology of combined
experimentation and logical argumentation did not spread immediately to other scientists.
Initial results were mixed. Bayon highlights how two scientists responded to Harvey’s
work differently. “Digby repeated some of Harvey’s tests with excised hearts and did
obtain a clear conception of the circulation,” Bayon explains, “while Descartes in his
Discours (1637) approved without really comprehending.”36 During the state of
transition that follow Harvey’s work, the scientists who had an open mind tended to catch
on to the methodology and its power quickly. Inversely, some scientists did not pay
attention, did not agree, or agreed but did not change. Sarton relates this well:
“Not only did the new method open the path to untold and unimaginable discoveries, but it
put an end to unprofitable quests and idle discussions; it broke the vicious circles wherein
philosophers had been obstinately turning for more than a thousand years. It was simple
enough in itself, but could not be understood as long as a series of intellectual prejudices
obscured man’s vision.”37
Those who did adopt the new methodology, however, found it rewarding. The
next major achievement in the study of the circulatory system was the discovery that
blood undergoes a change while passing through the lungs. This discovery was fueled
directly by Harvey’s experimental approach. Its originator described, “When venous
blood is received into a vessel, the surface and uppermost part of it takes on this scarlet
colour through exposure to the air.”38
36 Bayon, “Significance,” 451.37 George Sarton, The History of Science and the New Humanism (Cambridge: Harvard University Press, 1937), 101.38 Richard Lower, Tractatus de corde item de motu et colore sanguinis et chili in eum transitu, translated by Kenneth J. Franklin (Oxford: R. T. Gunther, 1935 [1669]). Vol 11, 168.
In the long term, Harvey’s method did become wide-spread in the study of
biology. Walter Pagel summarizes, “the scientific demonstration of blood circulation by
Harvey between 1615 and 1619 marks the foundation of modern scientific medicine.”39
Conclusion
We have described the scientific methodologies used before William Harvey’s
time, Harvey’s discoveries, the methodology he used to make those discoveries, the
people he inherited wisdom from, and his scientific legacy in biology. It was found that
Harvey was the first person to use experimental and logical methods to correctly induce a
significant discovery in biology. Furthermore, it was found that the method he used was
slowly adopted and is now widely used in medicine and biology.
Bibliography
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